Magnetic random access memory and manufacturing method of the same

ABSTRACT

A magnetic random access memory includes a magnetoresistive effect element which has a fixed layer, a recording layer and a non-magnetic layer provided between the fixed layer and the recording layer and in which the magnetization directions of the fixed layer and the recording layer are brought into a parallel state or an anti-parallel state in accordance with a direction of a current flowing between the fixed layer and the recording layer, a first contact which is connected to the recording layer and in which a contact area between the recording layer and the first contact is smaller than an area of the recording layer, and a cap layer which is provided between the first contact and the recording layer and which directly comes in contact with the first contact and which has a resistance higher than a resistance of the recording layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromprior Japanese Patent Application No. 2006-314127, filed Nov. 21, 2006,the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic random access memory (MRAM)of a spin injection magnetization reverse type, and a manufacturingmethod of the memory.

2. Description of the Related Art

In recent years, a magnetic random access memory (MRAM) of a spininjection magnetization reverse type has been expected as a low-currentMRAM technology of the next generation.

In the spin injection magnetization reverse type, for example, astructure of a 1Tr+1MTJ type is employed. In this structure of the1Tr+1MTJ type, an interconnect is connected to one end of a magnetictunnel junction (MTJ) element via a contact, and a transistor isconnected to the other end of the MTJ element. Here, the contact largelycomes into contact with the MTJ element. This is because the MTJ elementhaving a small area is assumed to reduce the current of spin injectionwriting.

However, to reverse magnetization of the MTJ element, spin electronsrequired for reversing the whole magnetization of the MTJ element needto be injected thereinto from a contact which is larger than the MTJelement. Therefore, lowering of the current of the memory can berealized. However, an amount of the current flowing through one MTJelement and one transistor increases, and this fact has beeninconvenient from a viewpoint of cell design.

It is to be noted that prior art document information concerned with theinvention of this application is as follows:

[Patent Document 1] Jpn. Pat. Appln. KOKAI Publication No. 2005-340300;

[Patent Document 2] Jpn. Pat. Appln. KOKAI Publication No. 2004-146821;and

[Patent Document 3] Jpn. Pat. Appln. KOKAI Publication No. 2006-120742.

BRIEF SUMMARY OF THE INVENTION

A magnetic random access memory according to a first aspect of thepresent invention comprises a magnetoresistive effect element whichincludes a fixed layer having a fixed magnetization direction, arecording layer having a reversible magnetization direction and anon-magnetic layer provided between the fixed layer and the recordinglayer and in which the magnetization directions of the fixed layer andthe recording layer are brought into a parallel state or ananti-parallel state in accordance with a direction of a current whichflows between the fixed layer and the recording layer; a first contactwhich is connected to the recording layer and in which a contact areabetween the recording layer and the first contact is smaller than anarea of the recording layer; and a cap layer which is provided betweenthe first contact and the recording layer and which directly comes incontact with the first contact and which has a resistance higher than aresistance of the recording layer.

A magnetic random access memory manufacturing method according to asecond aspect of the present invention comprises forming amagnetoresistive effect element having a fixed layer having a fixedmagnetization direction, a recording layer having a reversiblemagnetization direction and a non-magnetic layer provided between thefixed layer and the recording layer; forming a first insulating film onthe magnetoresistive effect element; covering the first insulating filmwith a second insulating film and removing the second insulating filmuntil the first insulating film is exposed; removing the firstinsulating film to form a groove; forming a third insulating film onlyon a side surface of the groove; and forming a contact in the groove, acontact area between the contact and the magnetoresistive effect elementbeing smaller than an area of the magnetoresistive effect element.

A magnetic random access memory manufacturing method according to athird aspect of the present invention comprises forming amagnetoresistive effect element having a fixed layer having a fixedmagnetization direction, a recording layer having a reversiblemagnetization direction and a non-magnetic layer provided between thefixed layer and the recording layer; forming a first insulating film onthe magnetoresistive effect element; covering the first insulating filmwith a second insulating film and removing the second insulating filmuntil the first insulating film is exposed; removing the firstinsulating film to form a groove; forming a contact having a hollowportion at the center thereof only on a side surface of the groove, acontact area between the contact and the magnetoresistive effect elementbeing smaller than an area of the magnetoresistive effect element; andforming a third insulating film at the hollow portion.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a sectional view showing a magnetic random access memoryaccording to a first embodiment of the present invention;

FIG. 2 shows a plan view and a sectional view in which a connectingportion between an MTJ element and a contact shown in FIG. 1 isenlarged;

FIGS. 3A to 3J are sectional views showing manufacturing steps of themagnetic random access memory according to the first embodiment of thepresent invention;

FIGS. 4A to 4D are explanatory views of a write operation of themagnetic random access memory according to the first embodiment of thepresent invention;

FIG. 5 is a sectional view showing a magnetic random access memoryaccording to a second embodiment of the present invention;

FIG. 6 shows a plan view and a sectional view in which a connectingportion between an MTJ element and a contact shown in FIG. 5 isenlarged;

FIGS. 7A to 7H are sectional views showing manufacturing steps of themagnetic random access memory according to the second embodiment of thepresent invention;

FIGS. 8A to 8D are explanatory views of a write operation of themagnetic random access memory according to the second embodiment of thepresent invention;

FIG. 9 is a sectional view showing a magnetic random access memoryaccording to a third embodiment of the present invention;

FIG. 10 shows a plan view and a sectional view in which a connectingportion between an MTJ element and a contact shown in FIG. 9 isenlarged;

FIGS. 11A to 11J are sectional views showing manufacturing steps of themagnetic random access memory according to the third embodiment of thepresent invention;

FIG. 12 is a sectional view showing a magnetic random access memoryaccording to a fourth embodiment of the present invention;

FIG. 13 shows a plan view and a sectional view in which a connectingportion between an MTJ element and a contact shown in FIG. 12 isenlarged;

FIGS. 14A to 14H are sectional views showing manufacturing steps of themagnetic random access memory according to the fourth embodiment of thepresent invention;

FIG. 15 is a sectional view showing a magnetic random access memoryaccording to a fifth embodiment of the present invention;

FIG. 16 shows a plan view and a sectional view in which a connectingportion between an MTJ element and a contact shown in FIG. 15 isenlarged;

FIGS. 17A to 17C are explanatory views of a write operation of themagnetic random access memory according to the fifth embodiment of thepresent invention;

FIG. 18 is a sectional view showing a magnetic random access memoryaccording to a sixth embodiment of the present invention;

FIG. 19 shows a plan view and a sectional view in which a connectingportion between an MTJ element and a contact shown in FIG. 18 isenlarged;

FIGS. 20A to 20C are explanatory views of a write operation of themagnetic random access memory according to the sixth embodiment of thepresent invention;

FIG. 21 is a sectional view showing a magnetic random access memoryaccording to a seventh embodiment of the present invention;

FIG. 22 shows a plan view and a sectional view in which a connectingportion between an MTJ element and a contact shown in FIG. 21 isenlarged;

FIGS. 23A to 23D are explanatory views of a write operation of themagnetic random access memory according to the seventh embodiment of thepresent invention;

FIG. 24 is a sectional view showing a magnetic random access memoryaccording to an eighth embodiment of the present invention;

FIG. 25 shows a plan view and a sectional view in which a connectingportion between an MTJ element and a contact shown in FIG. 24 isenlarged;

FIGS. 26A to 26D are explanatory views of a write operation of themagnetic random access memory according to the eighth embodiment of thepresent invention;

FIG. 27 is a sectional view showing a magnetic random access memoryaccording to a ninth embodiment of the present invention;

FIG. 28 shows a plan view and a sectional view in which a connectingportion between an MTJ element and a contact shown in FIG. 27 isenlarged;

FIGS. 29A to 29C are sectional views showing manufacturing steps of themagnetic random access memory according to the ninth embodiment of thepresent invention;

FIGS. 30A to 30C are sectional views of manufacturing steps for forminga structure of FIG. 29;

FIGS. 31A to 31C are sectional views of manufacturing steps for formingthe structure of FIG. 29;

FIG. 32 is a sectional view showing a magnetic random access memoryaccording to a tenth embodiment of the present invention; and

FIG. 33 shows a plan view and a sectional view in which a connectingportion between an MTJ element and a contact shown in FIG. 32 isenlarged.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention will hereinafter be described withreference to the drawings. In the description, portions common to allthe drawings are denoted with common reference numbers.

[1] Magnetic Random Access Memory

In a magnetic random access memory (MRAM) according to the embodiment ofthe present invention, a contact area of a contact is smaller than anarea of a magnetic tunnel junction (MTJ) element as a magnetoresistiveeffect element, at a portion where the MTJ element comes in contact withthe contact.

[1-1] First Embodiment

A first embodiment relates to a contact positioned above an MTJ element,and is an example in which this contact is formed to be thin, whereby acontact area of the contact with respect to a recording layer is set tobe smaller than an area of the recording layer.

(Structure)

FIG. 1 shows a sectional view of a magnetic random access memoryaccording to the first embodiment of the present invention. FIG. 2 showsa plan view and a sectional view in which a connecting portion betweenthe MTJ element and the contact shown in FIG. 1 is enlarged. Themagnetic random access memory according to the first embodiment of thepresent invention will hereinafter be described.

As shown in FIG. 1, a gate electrode 2 is formed on a semiconductorsubstrate (a silicon substrate) 1 via a gate insulating film (notshown), and source/drain dispersion layers 3 a, 3 b are formed in thesemiconductor substrate 1 on opposite sides of this gate electrode 2 toform a transistor (e.g., an MOS transistor) Tr which functions as aswitching unit.

A contact 4 is connected to the source/drain dispersion layer 3 a of thetransistor Tr, and an MTJ element MTJ is formed on this contact 4. TheMTJ element MTJ has a laminated structure in which a fixed layer (apinned layer) 11, a non-magnetic layer 12 and a recording layer (a freelayer) 13 are laminated in order. A cap layer 20 is formed on the MTJelement MTJ, and a contact 30 is directly connected to this cap layer20. Onto the contact 30, an interconnect 10 is connected. Thisinterconnect 10 is connected to, for example, a power terminal and aground terminal.

As shown in FIG. 2, the contact 30 is thinner than the MTJ element MTJ.Therefore, an area of a portion in which the contact 30 comes in contactwith the recording layer 13 via the cap layer 20 is smaller than that ofthe recording layer 13. The contact 30 is positioned at the center ofthe MTJ element MTJ (the recording layer 13). The MTJ element MTJ andthe contact 30 have a circular planar shape, and a diameter of thecontact 30 is smaller than that of the MTJ element MTJ.

It is preferable that the resistance of the cap layer 20 is, forexample, about one digit higher than that of the recording layer 13.Examples of a material of this cap layer 20 include a material of thenon-magnetic layer 12 and a barrier metal material having a large sheetresistance. Here, as the material of the non-magnetic layer 12, pleaserefer to paragraphs [2-2] described later. Examples of the barrier metalmaterial include the following materials (a) to (k):

(a) Ti;

(b) Ta;

(c) Ti-containing compounds (e.g., TiN, TiW, TiSiN, TiSi_(x), TiB₂, TiBand TiC);

(d) Ta-containing compounds (e.g., TaB₂, TaB, TaC, TaN, Ta₄N₅, Ta₅N₆,and Ta₂N);

(e) Zr-containing compounds (e.g., ZrB₂, ZrB, ZrC and ZrN);

(f) Hf-containing compounds (e.g., HfB, HfC and HfN);

(g) V-containing compounds (e.g., VB₂, VB, VC and VN);

(h) Nb-containing compounds (e.g., NbB₂, NbB, NbC and NbN);

(i) Cr-containing compounds (e.g., CrB₂, CrB, Cr₂B, Cr₃C₂, Cr₂N andCrN);

(j) Mo-containing compounds (e.g., MO₂B₃, MoB₂, MoB, Mo₂B, Mo_(x)C_(y),Mo₂C and MoN); and

(k) W-containing compounds (e.g., W_(x)B_(y), W₂B₅, W_(x)C_(y), WC, W₂C,W_(x)N_(y) and WN).

The cap layer 20 preferably has the same planar shape as that of the MTJelement MTJ from a viewpoint of easiness of a process, but it may have adifferent planar shape. An area of an upper surface (the surface on theside of the contact 30) of the cap layer 20 is preferably larger thanthat of a bottom surface (the surface on the side of the cap layer 20)of the contact 30.

(Manufacturing Method)

FIGS. 3A to 3J show sectional views of manufacturing steps of themagnetic random access memory according to the first embodiment of thepresent invention. A manufacturing method of the magnetic random accessmemory according to the first embodiment of the present invention willhereinafter be described. It is to be noted that steps after forming thecontact 4 to be connected to the transistor Tr will be described herein.

First, as shown in FIG. 3A, the fixed layer 11, the non-magnetic layer12, the recording layer 13, the cap layer 20 and a hard mask 21 aredeposited on the contact 4 in order. Here, since the cap layer 20 needsto have a resistance higher than that of the recording layer 13, the caplayer is made of, for example, an AlOx film, a TaN film or a TiN film.The hard mask 21 is made of, for example, a silicon nitride film or thelike.

Subsequently, as shown in FIG. 3B, the hard mask 21 is patterned into adesired shape by lithography and reactive ion etching (RIE). Then, thefixed layer 11, the non-magnetic layer 12, the recording layer 13 andthe cap layer 20 are etched using this hard mask 21. Consequently, theMTJ element MTJ having the desired shape is formed.

Next, as shown in FIG. 3C, an interlayer insulating film 22 made of, forexample, a silicon oxide film is deposited on the hard mask 21. Thisinterlayer insulating film 22 is deposited in such a film thickness asto cover the MTJ element MTJ.

Subsequently, as shown in FIG. 3D, the interlayer insulating film 22 isflattened by chemical mechanical polish (CMP) to expose the hard mask21. Here, it is preferable that when the hard mask 21 is exposed, arotation speed of the CMP changes, and hence different materials may beused in the hard mask 21 and the interlayer insulating film 22.

Subsequently, as shown in FIG. 3E, the hard mask 21 is selectivelyremoved to expose the cap layer 20. Consequently, a groove 23 is formed.Since this groove 23 is formed by removing the hard mask 21 used duringprocessing of the MTJ element MTJ, the groove has a size equal to thatof the MTJ element MTJ.

Subsequently, as shown in FIG. 3F, an insulating film 24 made of, forexample, a silicon nitride film is deposited in the groove 23. In thiscase, the insulating film 24 is formed in such a film thickness that thegroove 23 is not filled with the insulating film 24. The insulating film24 is preferably made of a material different from that of theinterlayer insulating film 22.

Subsequently, as shown in FIG. 3G, the insulating film 24 on a bottomsurface of the groove 23 and the interlayer insulating film 22 isremoved by anisotropic etching such as RIE. Consequently, the insulatingfilm 24 is left only on a sidewall of the groove 23.

Subsequently, as shown in FIG. 3H, a barrier metal film (not shown) isdeposited in the groove 23, and a conductive film 30 a of Cu or the likeis formed on this barrier metal film. As a result, the groove 23 isfilled up with the conductive film 30 a.

Subsequently, as shown in FIG. 3I, the conductive film 30 a and thebarrier metal film are flattened by the CMP to expose the interlayerinsulating film 22. Consequently, the contact 30 to be connected to theMTJ element MTJ is formed.

Subsequently, as shown in FIG. 3J, an upper interconnect 10 is formed onthe contact 30. In this manner, a semiconductor device according to thefirst embodiment is formed.

According to such a manufacturing method of the first embodiment, aftera process of forming a usual contact hole (the groove 23), a process ofleaving the insulating film 24 on the sidewall is performed, so that adiameter of the contact 30 can be reduced.

(Write Operation)

FIGS. 4A to 4D show explanatory views of a write operation of themagnetic random access memory according to the first embodiment of thepresent invention. The write operation of the magnetic random accessmemory according to the first embodiment of the present invention willhereinafter be described.

In the first embodiment, the write operation using spin injectionmagnetization reverse is performed. Therefore, in the MTJ element MTJ,magnetization directions of the fixed layer 11 and the recording layer13 are brought into a parallel state or an anti-parallel state inaccordance with a direction of a current I which flows between the fixedlayer 11 and the recording layer 13. This specific description is asfollows.

In a case where “1” data is written, the current I is passed in adirection from the fixed layer 11 of the MTJ element MTJ to therecording layer 13. That is, electrons e are injected from the side ofthe recording layer 13 toward the fixed layer 11. Consequently, thefixed layer 11 and the recording layer 13 are magnetized in reversedirections, and they become the anti-parallel state. Thishigh-resistance state Rap is defined as the “1” data.

On the other hand, in a case where “0” data is written, the current I ispassed in a direction from the recording layer 13 of the MTJ element MTJto the fixed layer 11. That is, the electrons e are injected from theside of the fixed layer 11 toward the recording layer 13. Consequently,the fixed layer 11 and the recording layer 13 are magnetized in the samedirection, and they become the parallel state. This low-resistance stateRp is defined as the “0” data.

The write operation using such a spin injection magnetization reversetechnology is performed in the structure of the first embodiment asfollows. It is to be noted that an example where the “1” data is writtenwith respect to the MTJ element MTJ in which the “0” data has beenwritten will be described herein.

First, it is assumed that as shown in FIG. 4A, the recording layer 13 ofthe MTJ element MTJ is magnetized upwards, and the magnetizations of thefixed layer 11 and the recording layer 13 have the parallel state (a “0”data state). Then, as shown in FIG. 4B, when the write current I ispassed in a direction from the fixed layer 11 to the recording layer 13,the magnetization of the recording layer 13 first reverses only at aportion where the write current I (the electrons) flows (a portion whichcomes in contact with the contact 30).

The write current I is passed as it is, whereby as shown in FIG. 4C,propagation is generated in the recording layer 13 owing to currentspin, and the magnetization of the recording layer 13 starts reversingin order from the center of the recording layer 13 to an end thereof. Asa result, as shown in FIG. 4D, the recording layer 13 is magnetizeddownwards on the whole, and the magnetizations of the fixed layer 11 andthe recording layer 13 become the anti-parallel state (a “1” datastate).

In such a write operation, when the contact 30 is processed to be small,the portion where the write current I flows is an only contact portionbetween the recording layer 13 and the contact 30. Therefore, the writecurrent I can be made low, and there is an advantage that the currentflowing through the transistor Tr or the like can be made low.

However, to realize this, it is preferable that the resistance of thecap layer 20 formed in order to protect the MTJ element MTJ issufficiently higher than that of the recording layer 13. When such ahigh-resistance cap layer 20 is not disposed, the electrons arepropagated to the cap layer 20 faster than to the recording layer 13,and hence the write current I is not concentrated only on a contactportion between the contact 30 and the recording layer 13.

(Read Operation)

In a read operation of the first embodiment, a magnetoresistive effectis used.

The transistor Tr connected to the MTJ element MTJ of a selected cell isturned on, and a read current is passed from, for example, theinterconnect 10 to the transistor Tr through the MTJ element MTJ. Then,the “1” data and the “0” data are distinguished by the resistance of theMTJ element MTJ read based on this read current.

It is to be noted that during the read operation, a constant voltage maybe applied to read the current, or a constant current may be supplied toread the voltage.

[1-2] Second Embodiment

A second embodiment is an example in which the contact of the firstembodiment is arranged under an MTJ element. It is to be noted that inthe second embodiment, description of respects similar to those of theother embodiments is omitted.

(Structure)

FIG. 5 shows a sectional view of a magnetic random access memoryaccording to the second embodiment of the present invention. FIG. 6shows a plan view and a sectional view in which a connecting portionbetween an MTJ element and a contact is enlarged. The magnetic randomaccess memory according to the second embodiment of the presentinvention will hereinafter be described.

As shown in FIGS. 5 and 6, the second embodiment is different from thefirst embodiment in a position of a contact 40 having an area set to besmaller than that of a recording layer 13. That is, in the firstembodiment, the contact area of the contact 30 arranged on the side ofthe interconnect 10 is reduced, whereas in the second embodiment, acontact area of the contact 40 arranged on the side of a transistor Tris reduced. Furthermore, in the first embodiment, the fixed layer 11 isarranged on the side of the transistor Tr and the recording layer 13 isarranged on the side of the interconnect 10, whereas in the secondembodiment, a fixed layer 11 is arranged on the side of an interconnect10 and the recording layer 13 is arranged on the side of the transistorTr.

An area of a portion of the contact 40 which comes in contact with therecording layer 13 via a cap layer 20 is smaller than that of therecording layer 13. The contact 40 is positioned at the center of an MTJelement MTJ (the recording layer 13).

The cap layer 20 having a resistance higher than that of the recordinglayer 13 is formed between the contact 40 and the recording layer 13. Aplanar shape of the cap layer 20 may be the same as that of the MTJelement MTJ, or may be larger than that of the MTJ element MTJ (see FIG.7H). It is preferable that an area of a bottom surface (the surface onthe side of the contact 40) of the cap layer 20 is larger than that ofan upper surface (the surface on the side of the cap layer 20) of thecontact 40.

(Manufacturing Method)

FIGS. 7A to 7H show sectional views of manufacturing steps of themagnetic random access memory according to the second embodiment of thepresent invention. A manufacturing method of the magnetic random accessmemory according to the second embodiment of the present invention willhereinafter be described. It is to be noted that steps after forming acontact 4 to be connected to the transistor Tr will be described herein.

First, as shown in FIG. 7A, the contact 4 to be connected to atransistor (not shown) is formed on a semiconductor substrate (notshown).

Subsequently, as shown in FIG. 7B, an insulating film 41 made of, forexample, a silicon oxide film is formed on the contact 4, and thisinsulating film 41 is processed. Consequently, a groove 42 is formed soas to expose the contact 4.

Subsequently, as shown in FIG. 7C, an insulating film 43 made of, forexample, a silicon nitride film is deposited in the groove 42. In thiscase, the insulating film 43 is formed in such a film thickness that thegroove 42 is not filled with the insulating film 43. The insulating film43 is preferably made of a material different from that of theinsulating film 41.

Subsequently, as shown in FIG. 7D, a bottom surface of the groove 42 andthe insulating film 43 on the insulating film 41 are removed byanisotropic etching such as RIE. Consequently, the insulating film 43 isleft only on a sidewall of the groove 42.

Subsequently, as shown in FIG. 7E, a barrier metal film (not shown) isdeposited in the groove 42, and a conductive film 40 a of Cu or the likeis formed on this barrier metal film. Afterward, the conductive film 40a and the barrier metal film are flattened by CMP to expose theinsulating film 41. Consequently, the contact 40 is formed.

Subsequently, as shown in FIG. 7F, the cap layer 20 is formed on thecontact 40, and this cap layer 20 is patterned into a desired shape.Here, since the cap layer 20 needs to have a resistance higher than thatof the recording layer 13, the layer is made of, for example, an AlOxfilm, a TaN film or a TiN film.

Subsequently, as shown in FIG. 7G, on the cap layer 20, the recordinglayer 13, a non-magnetic layer 12 and the fixed layer 11 are depositedin order. Afterward, the fixed layer 11, the non-magnetic layer 12 andthe recording layer 13 are etched. Consequently, the MTJ element MTJhaving the desired shape is formed. It is to be noted that the cap layer20 is not processed in the step of FIG. 7F, and may collectively beprocessed simultaneously with the MTJ element MTJ in the present step.

Subsequently, as shown in FIG. 7H, an upper interconnect 10 is formed onthe MTJ element MTJ. In this manner, a semiconductor device according tothe second embodiment is formed.

According to such a manufacturing method of the second embodiment, aftera process of forming a usual contact hole (the groove 42), a process ofleaving the insulating film 43 on the sidewall is performed, so that adiameter of the contact 40 can be reduced.

Furthermore, in the first embodiment, as shown in FIG. 3G, in the stepof leaving the insulating film 24 on the sidewall, the etching of theinsulating film 24 needs to be stopped by the cap layer 20, and amagnetic metal of a portion of the MTJ element MTJ which comes incontact with the contact 30 might be damaged. On the other hand, in thesecond embodiment, in the step of leaving the insulating film 43 on thesidewall, the cap layer 20 does not function as an underlayer, and theMTJ element MTJ is formed above the contact 40, so that there is anadvantage that unlike the first embodiment, the magnetic metal might notbe damaged.

(Write Operation)

FIGS. 8A to 8D show explanatory views of a write operation of themagnetic random access memory according to the second embodiment of thepresent invention. The write operation of the magnetic random accessmemory according to the second embodiment of the present invention willhereinafter be described. It is to be noted that a case where “1” datais written in the MTJ element MTJ in which “0” data has been writtenwill be described as an example herein.

First, it is assumed that as shown in FIG. 8A, the recording layer 13 ofthe MTJ element MTJ is magnetized downwards, and the magnetizations ofthe fixed layer 11 and the recording layer 13 have a parallel state (a“0” data state). Then, as shown in FIG. 8B, when a write current I ispassed in a direction from the fixed layer 11 to the recording layer 13,the magnetization of the recording layer 13 first reverses only at aportion where the write current I (electrons) flows (a portion whichcomes in contact with the contact 40). The write current I is passed asit is, whereby as shown in FIG. 8C, propagation is generated in therecording layer 13 owing to current spin, and the magnetization of therecording layer 13 starts reversing in order from the center of therecording layer 13 to an end thereof. As a result, as shown in FIG. 8D,the recording layer 13 is magnetized upwards on the whole, and themagnetizations of the fixed layer 11 and the recording layer 13 have ananti-parallel state (a “1” data state).

In such a write operation, when the contact 40 is processed to be small,the portion where the write current I flows is an only contact portionbetween the recording layer 13 and the contact 40. Therefore, in thesame manner as in the first embodiment, the write current I can be madelow, and there is an advantage that the current flowing through thetransistor Tr or the like can be made low.

[1-3] Third Embodiment

A third embodiment relates to a contact positioned above an MTJ element,and is an example in which this contact is provided with a hollowportion at the center of the contact, whereby a contact area of thecontact with respect to a recording layer is set to be smaller than anarea of the recording layer. It is to be noted that in the thirdembodiment, description of respects similar to those of the otherembodiments is omitted.

(Structure)

FIG. 9 shows a sectional view of a magnetic random access memoryaccording to the third embodiment of the present invention. FIG. 10shows a plan view and a sectional view in which a connecting portionbetween an MTJ element and a contact of FIG. 9 is enlarged. The magneticrandom access memory according to the third embodiment of the presentinvention will hereinafter be described.

As shown in FIGS. 9 and 10, the third embodiment is different from thefirst embodiment in a shape of a contact 30 having an area set to besmaller than that of a recording layer 13. That is, to set the contactarea of the contact 30 with respect to the recording layer 13 to besmaller than the area of the recording layer 13, in the firstembodiment, the contact 30 is thinned, whereas a hollow portion 30′ isformed at the center of the contact 30 in the third embodiment.

The contact 30 of the third embodiment is cylindrical, because thehollow portion 30′ is present at the center. An insulating film 24 isformed in this hollow portion 30′. As shown in the drawing, an outerside surface of the contact 30 may match with side surfaces of an MTJelement MTJ and a cap layer 20, but may not match with the side surfacesof the MTJ element MTJ and the cap layer 20.

(Manufacturing Method)

FIGS. 11A to 11J show sectional views of manufacturing steps of themagnetic random access memory according to the third embodiment of thepresent invention. A manufacturing method of the magnetic random accessmemory according to the third embodiment of the present invention willhereinafter be described. It is to be noted that steps after forming acontact 4 to be connected to a transistor Tr will be described herein.

First, as shown in FIG. 11A, on the contact 4, a fixed layer 11, anon-magnetic layer 12, the recording layer 13, the cap layer 20 and ahard mask 21 are deposited in order. Here, since the cap layer 20 needsto have a resistance higher than that of the recording layer 13, thelayer is made of, for example, an AlOx film, a TaN film or a TiN film.The hard mask 21 is made of, for example, a silicon nitride film.

Subsequently, as shown in FIG. 11B, the hard mask 21 is patterned into adesired shape by lithography and RIE. Then, the fixed layer 11, thenon-magnetic layer 12, the recording layer 13 and the cap layer 20 areetched using this hard mask 21. Consequently, the MTJ element MTJ havingthe desired shape is formed.

Subsequently, as shown in FIG. 11C, an interlayer insulating film 22made of, for example, a silicon oxide film is deposited on the hard mask21. This interlayer insulating film 22 is deposited in such a filmthickness as to cover the MTJ element MTJ.

Subsequently, as shown in FIG. 1D, the interlayer insulating film 22 isflattened by CMP to expose the hard mask 21. Here, it is preferable thatwhen the hard mask 21 is exposed, a rotation speed of the CMP changes,and hence different materials may be used in the hard mask 21 and theinterlayer insulating film 22.

Subsequently, as shown in FIG. 11E, the hard mask 21 is selectivelyremoved to expose the cap layer 20. Consequently, a groove 23 is formed.Since this groove 23 is formed by removing the hard mask 21 used duringprocessing of the MTJ element MTJ, the groove has a size equal to thatof the MTJ element MTJ.

Subsequently, as shown in FIG. 11F, a barrier metal film (not shown) isdeposited in the groove 23, and a conductive film 30 a of Cu or the likeis deposited on this barrier metal film. In this case, the conductivefilm 30 a is formed in such a film thickness that the groove 23 is notfilled with the conductive film 30 a.

Subsequently, as shown in FIG. 11G, the conductive film 30 a on a bottomsurface of the groove 23 and the interlayer insulating film 22 isremoved by anisotropic etching such as RIE. Consequently, the conductivefilm 30 a is left only on a sidewall of the groove 23, and the contact30 having the hollow portion 30′ is formed.

Subsequently, as shown in FIG. 11H, the insulating film 24 made of asilicon nitride film is formed in the hollow portion 30′. Consequently,the hollow portion 30′ of the contact 30 is filled up with theinsulating film 24. This insulating film 24 is preferably made of amaterial different from that of the interlayer insulating film 22.

Subsequently, as shown in FIG. 11I, the insulating film 24 is flattenedby the CMP to expose the interlayer insulating film 22.

Subsequently, as shown in FIG. 11J, an upper interconnect 10 is formedon the contact 30. In this manner, a semiconductor device according tothe third embodiment is formed.

According to such a manufacturing method of the third embodiment, aftera process of forming a usual contact hole (the groove 23), a process ofleaving the conductive film 30 a on the sidewall is performed, so thatthe contact 30 having the hollow portion 30′ can be formed, and acontact area between the contact 30 and the recording layer 13 can bereduced.

Moreover, in the first embodiment, as shown in FIG. 3G, in the processof leaving the insulating film 24 on the sidewall, the etching of theinsulating film 24 needs to be stopped by the cap layer 20, and amagnetic metal of a portion of the MTJ element MTJ which comes incontact with the contact 30 might be damaged. On the other hand, in thethird embodiment, since the contact 30 itself is formed in the step ofleaving the contact on the sidewall, it can be avoided that the magneticmetal of the portion of the MTJ element MTJ which comes in contact withthe contact 30 is damaged, so that satisfactory contact can be realized.

It is to be noted that in the present embodiment, write and readoperations similar to those of the first embodiment can be realized.Here, in the first embodiment, since a contact portion between therecording layer 13 and the contact 30 is positioned at the center of therecording layer 13, propagation of current spin is generated from thecenter of the recording layer 13 toward end portions. On the other hand,in the present embodiment, the propagation of the current spin isgenerated from a periphery of the recording layer 13 toward the centerthereof. Therefore, the reverse is carried out from the periphery of therecording layer 13, and hence there are many reverse sources and themagnetization is easily reversed. Owing to the reverse of themagnetization from the periphery of the recording layer 13, an abnormalfixed state of the magnetization which is called Vortex is not easilygenerated.

[1-4] Fourth Embodiment

A fourth embodiment is an example in which the contact of the thirdembodiment is arranged under an MTJ element. It is to be noted that inthe fourth embodiment, description of respects similar to those of theother embodiments is omitted.

(Structure)

FIG. 12 shows a sectional view of a magnetic random access memoryaccording to the fourth embodiment of the present invention. FIG. 13shows a plan view and a sectional view in which a connecting portionbetween the MTJ element and a contact shown in FIG. 12 is enlarged. Themagnetic random access memory according to the fourth embodiment of thepresent invention will hereinafter be described.

As shown in FIGS. 12 and 13, the fourth embodiment is different from thethird embodiment in a position of a contact 40 formed to be smaller thanan area of a recording layer 13. That is, in the third embodiment, acontact area of the contact 30 arranged on an interconnect 10 side isreduced, whereas in the fourth embodiment, a contact area of the contact40 arranged on a transistor Tr side is reduced. Furthermore, in thethird embodiment, a fixed layer 11 is arranged on the transistor Tr sideand the recording layer 13 is arranged on the interconnect 10 side,whereas in the fourth embodiment, the fixed layer 11 is arranged on theinterconnect 10 side and the recording layer 13 is arranged on thetransistor Tr side.

The contact 40 of the fourth embodiment is cylindrical, because a hollowportion 40′ is present at the center of the contact. An insulating film43 is formed in this hollow portion 40′. An outer side surface of thecontact 40 may match with side surfaces of an MTJ element MTJ and a caplayer 20 (see FIGS. 12 and 13), or may not match with the side surfacesof the MTJ element MTJ and the cap layer 20. For example, the sidesurface of the cap layer 20 may protrude from the outer side surface ofthe contact 40 (see FIG. 14G).

(Manufacturing Method)

FIGS. 14A to 14H show sectional views of manufacturing steps of themagnetic random access memory according to the fourth embodiment of thepresent invention. A manufacturing method of the magnetic random accessmemory according to the fourth embodiment of the present invention willhereinafter be described. It is to be noted that steps after forming acontact 4 to be connected to the transistor Tr will be described herein.

First, as shown in FIG. 14A, the contact 4 to be connected to atransistor (not shown) is formed on a semiconductor substrate (notshown).

Subsequently, as shown in FIG. 14B, an insulating film 41 made of, forexample, a silicon oxide film is formed on the contact 4, and thisinsulating film 41 is processed. Consequently, a groove 42 is formed toexpose the contact 4.

Subsequently, as shown in FIG. 14C, a barrier metal film (not shown) isdeposited in the groove 42, and a conductive film 40 a of Cu or the likeis formed on this barrier metal film.

Subsequently, as shown in FIG. 14D, the barrier metal film and theconductive film 40 a on the contact 4 and the insulating film 41 areremoved by anisotropic etching such as RIE. Consequently, the contact 40having the hollow portion 40′ is formed.

Subsequently, as shown in FIG. 14E, the insulating film 43 made of, forexample, a silicon nitride film is deposited in the hollow portion 40′.Afterward, the insulating film 43 is flattened by CMP to expose theinsulating film 41. Here, the insulating film 43 is preferably made of amaterial different from that of the insulating film 41.

Subsequently, as shown in FIG. 14F, the cap layer 20 is formed on thecontact 40, and this cap layer 20 is patterned into a desired shape.Here, since the cap layer 20 needs to have a resistance higher than therecording layer 13, the cap layer is made of, for example, an AlOx film,a TaN film or a TiN film.

Subsequently, as shown in FIG. 14G, the recording layer 13, anon-magnetic layer 12 and the fixed layer 11 are deposited on the caplayer 20 in order. Afterward, the fixed layer 11, the non-magnetic layer12 and the recording layer 13 are etched. Consequently, the MTJ elementMTJ having the desired shape is formed. It is to be noted that the caplayer 20 may not be processed in the step of FIG. 14F, and maycollectively be processed together with the MTJ element MTJ in thepresent step.

Subsequently, as shown in FIG. 14H, the upper interconnect 10 is formedon the MTJ element MTJ. In this manner, a semiconductor device of thefourth embodiment is formed.

According to the manufacturing method of the fourth embodiment, after aprocess to form a usual contact hole (the groove 42), a process to leavethe conductive film 40 a on a sidewall is performed, so that the contact40 having the hollow portion 40′ can be formed, and a contact areabetween the contact 40 and the recording layer 13 can be reduced.

Moreover, in the fourth embodiment, during the CMP (FIG. 14E) of theinsulating film 43 to fill in the hollow portion 40′ of the contact 40,the conductive film 40 a of the contact 40 can be used as a stopperlayer. Therefore, stability of control of the CMP improves, flatness ofan underlayer portion of the MTJ element MTJ increases, anddeterioration of a magnetic property of the MTJ element MTJ due tofluctuation of an underlayer can be inhibited.

[1-5] Fifth Embodiment

A fifth embodiment relates to a contact positioned above an MTJ element,and is an example in which this contact and the MTJ element aremisaligned to set a contact area of the contact with respect to arecording layer to be smaller than an area of the recording layer. It isto be noted that in the fifth embodiment, description of respectssimilar to those of the other embodiments is omitted.

(Structure)

FIG. 15 shows a sectional view of a magnetic random access memoryaccording to the fifth embodiment of the present invention. FIG. 16shows a plan view and a sectional view in which a connecting portionbetween the MTJ element and the contact shown in FIG. 15 is enlarged.The magnetic random access memory according to the fifth embodiment ofthe present invention will hereinafter be described.

As shown in FIGS. 15 and 16, the fifth embodiment is different from thefirst embodiment in a method of setting a contact area of a contact 30with respect to a recording layer 13 to be smaller than an area of therecording layer 13. That is, in the first embodiment, the contact 30 isreduced, whereas in the fifth embodiment, the contact 30 itself is notreduced, and center C2 of the contact 30 is arranged to sift from centerC1 of an MTJ element MTJ.

The area of the contact 30 of the fifth embodiment is equal to that ofthe MTJ element MTJ. It is preferable that sift S between the center C2of the contact 30 and the center C1 of the MTJ element MTJ is ½ or moreof a width (e.g., a minimum processing dimension F) of the MTJ elementMTJ in a short direction (a magnetization difficult-axis direction).

It is to be noted that an accidental misalignment due to usuallithography is about ¼ of the minimum processing dimension F.

According to such a fifth embodiment, the contact 30 is formed in ausual size, and this contact 30 may be formed so as to sift from the MTJelement MTJ. Therefore, as compared with the first embodiment, steps ofa sidewall leaving process and the like can be omitted, and hence thereis an advantage that processes are facilitated.

(Write Operation)

FIGS. 17A to 17C show explanatory views of a write operation of themagnetic random access memory according to the fifth embodiment of thepresent invention. The write operation of the magnetic random accessmemory according to the fifth embodiment of the present invention willhereinafter be described. It is to be noted that a case where “1” datais written in the MTJ element MTJ in which “0” data has been writtenwill be described as an example herein.

First, it is assumed that as shown in FIG. 17A, the recording layer 13of the MTJ element MTJ is magnetized upwards, and the magnetizations ofa fixed layer 11 and the recording layer 13 have a parallel state (a “0”data state). Then, as shown in FIG. 17B, when a write current I ispassed in a direction from the fixed layer 11 to the recording layer 13,the magnetization of the recording layer 13 first reverses only at aportion where the write current I (electrons) flows (a portion whichcomes in contact with the contact 30). The write current I is passed asit is, whereby propagation is generated in the recording layer 13 owingto current spin, and the magnetization of the recording layer 13 startsreversing in order from an end of the recording layer 13 toward thewhole layer.

As a result, as shown in FIG. 17C, the recording layer 13 is magnetizeddownwards on the whole, and the magnetizations of the fixed layer 11 andthe recording layer 13 have an anti-parallel state (binary 1 state).

In such a write operation, when the contact 30 is misaligned withrespect to the MTJ element MTJ, the portion where the write current Iflows is an only contact portion between the recording layer 13 and thecontact 30. Therefore, in the same manner as in the first embodiment,the write current I can be made low, and there is an advantage that thecurrent flowing through the transistor Tr can be made low.

Moreover, in the first embodiment and the like, since the contactportion between the recording layer 13 and the contact 30 is positionedat the center of the recording layer 13, the propagation of the currentspin is generated from the center of the recording layer 13 toward anend portion thereof. On the other hand, since the misalignment is usedin the present embodiment, the contact portion between the recordinglayer 13 and the contact 30 is positioned at the end portion of therecording layer 13. Therefore, in the present embodiment, thepropagation of the current spin is generated from the end of therecording layer 13 toward the whole layer. Consequently, fixing of anintermediate state (a state in which an intermediate resistance value istaken from binary resistance values of “1”, “0”) due to a magneticdomain does not easily occur. Furthermore, in the present embodiment,the contact 30 is easily processed as compared with the firstembodiment.

[1-6] Sixth Embodiment

A sixth embodiment is an example in which the contact of the fifthembodiment is arranged under an MTJ element. It is to be noted that inthe sixth embodiment, description of respects similar to those of theother embodiments is omitted.

(Structure)

FIG. 18 shows a sectional view of a magnetic random access memoryaccording to the sixth embodiment of the present invention. FIG. 19shows a plan view and a sectional view in which a connecting portionbetween the MTJ element and the contact shown in FIG. 18 is enlarged.The magnetic random access memory according to the sixth embodiment ofthe present invention will hereinafter be described.

As shown in FIGS. 18 and 19, the sixth embodiment is different from thefifth embodiment in a position of a contact 40 to be misaligned with anMTJ element MTJ. That is, in the fifth embodiment, the contact 30arranged on an interconnect 10 side is misaligned, whereas in the sixthembodiment, the contact 40 arranged on a transistor Tr side ismisaligned. Furthermore, in the fifth embodiment, the fixed layer 11 isarranged on the transistor Tr side and the recording layer 13 isarranged on the interconnect 10 side, whereas in the sixth embodiment, afixed layer 11 is arranged on an interconnect 10 side and a recordinglayer 13 is arranged on a transistor Tr side.

An area of the contact 40 of the sixth embodiment is equal to that ofthe MTJ element MTJ. It is preferable that sift S between center C2 ofthe contact 40 and center C1 of the MTJ element MTJ is, for example, ½or more of a width (e.g., a minimum processing dimension F) of the MTJelement MTJ in a short direction (a magnetization difficult-axisdirection). It is to be noted that an accidental misalignment due tousual lithography is about ¼ of the minimum processing dimension F.

According to such a sixth embodiment, the contact 40 is formed in ausual size, and this contact 40 may be formed so as to sift from the MTJelement MTJ. Therefore, as compared with the second embodiment, steps ofa sidewall leaving process and the like can be omitted, and hence thereis an advantage that processes are facilitated.

(Write Operation)

FIGS. 20A to 20C show explanatory views of a write operation of themagnetic random access memory according to the sixth embodiment of thepresent invention. The write operation of the magnetic random accessmemory according to the sixth embodiment of the present invention willhereinafter be described. It is to be noted that a case where “1” datais written in the MTJ element MTJ in which “0” data has been writtenwill be described as an example herein.

First, it is assumed that as shown in FIG. 20A, the recording layer 13of the MTJ element MTJ is magnetized downwards, and the magnetizationsof the fixed layer 11 and the recording layer 13 have a parallel state(a “0” data state). Then, as shown in FIG. 20B, when a write current Iis passed in a direction from the fixed layer 11 to the recording layer13, the magnetization of the recording layer 13 first reverses only at aportion where the write current I (electrons) flows (a portion whichcomes in contact with the contact 40). The write current I is passed asit is, whereby propagation is generated in the recording layer 13 owingto current spin, and the magnetization of the recording layer 13 startsreversing in order from an end of the recording layer 13 toward thewhole layer. As a result, as shown in FIG. 20C, the recording layer 13is magnetized upwards on the whole, and the magnetizations of the fixedlayer 11 and the recording layer 13 have an anti-parallel state (a “1”data state).

In such a write operation, when the contact 40 is misaligned withrespect to the MTJ element MTJ, the portion where the write current Iflows is an only contact portion between the recording layer 13 and thecontact 40. Therefore, in the same manner as in the second embodiment,the write current I can be made low, and there is an advantage that thecurrent flowing through the transistor Tr can be made low.

Moreover, in the second embodiment and the like, since the contactportion between the recording layer 13 and the contact 40 is positionedat the center of the recording layer 13, the propagation of the currentspin is generated from the center of the recording layer 13 toward anend portion thereof. On the other hand, since the misalignment is usedin the present embodiment, the contact portion between the recordinglayer 13 and the contact 40 is positioned at the end portion of therecording layer 13. Therefore, in the present embodiment, thepropagation of the current spin is generated from the end of therecording layer 13 toward the whole layer.

[1-7] Seventh Embodiment

A seventh embodiment is a modification of the fifth embodiment, and isan example in which a contact to be misaligned itself is reduced. It isto be noted that in the seventh embodiment, description of respectssimilar to those of the other embodiments is omitted.

(Structure)

FIG. 21 shows a sectional view of a magnetic random access memoryaccording to the seventh embodiment of the present invention. FIG. 22shows a plan view and a sectional view in which a connecting portionbetween an MTJ element and the contact shown in FIG. 21 is enlarged. Themagnetic random access memory according to the seventh embodiment of thepresent invention will hereinafter be described.

As shown in FIGS. 21 and 22, the seventh embodiment is different fromthe fifth embodiment in that a contact 30 to be misaligned itself isreduced. An area of this contact 30 is smaller than that of an MTJelement MTJ. It is preferable that sift S between center C2 of thecontact 30 and center C1 of the MTJ element MTJ is, for example, ¼F orless of a width (e.g., a minimum processing dimension F) of the MTJelement MTJ in a short direction (a magnetization difficult-axisdirection). This is because when the sift is of this degree, adisadvantage due to misalignment is not generated.

(Write Operation)

FIGS. 23A to 23D show explanatory views of a write operation of themagnetic random access memory according to the seventh embodiment of thepresent invention. The write operation of the magnetic random accessmemory according to the seventh embodiment of the present invention willhereinafter be described. It is to be noted that a case where “1” datais written in the MTJ element MTJ in which “0” data has been writtenwill be described as an example herein.

First, it is assumed that as shown in FIG. 23A, a recording layer 13 ofthe MTJ element MTJ is magnetized upwards, and the magnetizations of afixed layer 11 and the recording layer 13 have a parallel state (a “0”data state). Then, as shown in FIG. 23B, when a write current I ispassed in a direction from the fixed layer 11 to the recording layer 13,the magnetization of the recording layer 13 first reverses only at aportion where the write current I (electrons) flows (a portion whichcomes in contact with the contact 30). The write current I is passed asit is, whereby as shown in FIG. 23C, propagation is generated in therecording layer 13 owing to current spin, and the magnetization of therecording layer 13 starts reversing in order from a contact portion ofthe recording layer 13 toward the whole layer. As a result, as shown inFIG. 23D, the recording layer 13 is magnetized downwards on the whole,and the magnetizations of the fixed layer 11 and the recording layer 13have an anti-parallel state (a “1” data state).

In such a write operation, the portion where the write current I flowsis an only contact portion between the recording layer 13 and thecontact 30. Therefore, in the same manner as in the first embodiment,the write current I can be made low, and there is an advantage that thecurrent flowing through the transistor Tr can be made low.

[1-8] Eighth Embodiment

An eighth embodiment is a modification of the sixth embodiment, and anexample in which a contact to be misaligned itself is reduced. It is tobe noted that in the eighth embodiment, description of respects similarto those of the other embodiments is omitted.

(Structure)

FIG. 24 shows a sectional view of a magnetic random access memoryaccording to the eighth embodiment of the present invention. FIG. 25shows a plan view and a sectional view in which a connecting portionbetween an MTJ element and the contact shown in FIG. 24 is enlarged. Themagnetic random access memory according to the eighth embodiment of thepresent invention will hereinafter be described.

As shown in FIGS. 24 and 25, the eighth embodiment is different from thesixth embodiment in that a contact 40 to be misaligned itself isreduced. An area of this contact 40 is smaller than that of an MTJelement MTJ. It is preferable that sift S between center C2 of thecontact 40 and center C1 of the MTJ element MTJ is, for example, ¼F orless of a width (e.g., a minimum processing dimension F) of the MTJelement MTJ in a short direction (a magnetization difficult-axisdirection). This is because when the sift is of this degree, adisadvantage due to misalignment is not generated.

(Write Operation)

FIGS. 26A to 26D show explanatory views of a write operation of themagnetic random access memory according to the eighth embodiment of thepresent invention. The write operation of the magnetic random accessmemory according to the eighth embodiment of the present invention willhereinafter be described. It is to be noted that a case where “1” datais written in the MTJ element MTJ in which “0” data has been writtenwill be described as an example herein.

First, it is assumed that as shown in FIG. 26A, a recording layer 13 ofthe MTJ element MTJ is magnetized downwards, and the magnetizations of afixed layer 11 and the recording layer 13 have a parallel state (a “0”data state). Then, as shown in FIG. 26B, when a write current I ispassed in a direction from the fixed layer 11 to the recording layer 13,the magnetization of the recording layer 13 first reverses only at aportion where the write current I (electrons) flows (a portion whichcomes in contact with the contact 40). The write current I is passed asit is, whereby as shown in FIG. 26C, propagation is generated in therecording layer 13 owing to current spin, and the magnetization of therecording layer 13 starts reversing in order from a contact portion ofthe recording layer 13 toward the whole layer. As a result, as shown inFIG. 26D, the recording layer 13 is magnetized upwards on the whole, andthe magnetizations of the fixed layer 11 and the recording layer 13 havean anti-parallel state (a “1” data state).

In such a write operation, the portion where the write current I flowsis an only contact portion between the recording layer 13 and thecontact 40. Therefore, in the same manner as in the second embodiment,the write current I can be made low, and there is an advantage that thecurrent flowing through the transistor Tr can be made low.

[1-9] Ninth Embodiment

A ninth embodiment relates to a contact positioned above an MTJ element,and is an example in which this contact is linearly formed, whereby acontact area of the contact with respect to a recording layer is set tobe smaller than an area of the recording layer. It is to be noted thatin the ninth embodiment, description of respects similar to those of theother embodiments is omitted.

(Structure)

FIG. 27 shows a sectional view of a magnetic random access memoryaccording to the ninth embodiment of the present invention. FIG. 28shows a plan view and a sectional view in which a connecting portionbetween an MTJ element and a contact of FIG. 27 is enlarged. Themagnetic random access memory according to the ninth embodiment of thepresent invention will hereinafter be described.

As shown in FIGS. 27 and 28, the ninth embodiment is different from thefirst embodiment in a shape of a contact 30 having an area set to besmaller than that of a recording layer 13. That is, to set the contactarea of the contact 30 with respect to the recording layer 13 to besmaller than the area of the recording layer 13, in the firstembodiment, one thin contact 30 is formed, whereas in the ninthembodiment, two linear thin contacts 30-1, 30-2 are formed. The contacts30-1, 30-2 are arranged away from each other, and a gap between thesecontacts 30-1 and 30-2 is filled up with an insulating film 24.

(Manufacturing Method)

FIGS. 29A to 29C show plan views of manufacturing steps of the magneticrandom access memory according to the ninth embodiment of the presentinvention. FIGS. 30A to 30C are sectional views of manufacturing stepsfor forming a structure of FIG. 29. FIGS. 31A to 31C are sectional viewsof manufacturing steps for forming the structure of FIG. 29. Amanufacturing method of the magnetic random access memory according tothe ninth embodiment of the present invention will hereinafter bedescribed.

First, as shown in FIG. 29A, on an MTJ element MTJ, the linearinsulating film 24 and a metal film 30 a are formed. This formation isrealized by, for example, the following first and second methods.

In the first method, as shown in FIG. 30A, the metal film 30 a is formedin a linear groove 23. Subsequently, as shown in FIG. 30B, the metalfilm 30 a is etched, and the metal film 30 a is left only on a sidesurface of the groove 23. Afterward, the groove 23 is filled up with theinsulating film 24. Consequently, the linear insulating film 24 and themetal film 30 a are formed.

In the second method, as shown in FIG. 31A, the linear insulating film24 is formed on a cap layer 20, and the metal film 30 a is formed onthis insulating film 24. Subsequently, as shown in FIG. 31B, the metalfilm 30 a is etched so as to be left only on a side surface of theinsulating film 24. Consequently, the linear insulating film 24 and themetal film 30 a are formed. Afterward, as shown in FIG. 31C, a peripheryof the metal film 30 a is filled up with an insulating film 51.

Subsequently, as shown in FIG. 29B, a resist 50 is formed so as to crossthe linear insulating film 24 and the metal film 30 a.

Subsequently, as shown in FIG. 29C, the insulating film 24 and the metalfilm 30 a are etched using the resist 50 as a mask. As a result, twolinear contacts 30-1, 30-2 are formed on the MTJ element MTJ. Afterward,the resist 50 is removed.

According to such a manufacturing method of the ninth embodiment, thelinear contacts 30-1, 30-2 are formed by a sidewall leaving process.Therefore, fine processing can be performed as compared with a casewhere the contacts are formed by lithography.

[1-10] Tenth Embodiment

A tenth embodiment is a combination of the first and second embodiments,and an example in which contacts above and under an MTJ element arereduced. It is to be noted that in the tenth embodiment, description ofrespects similar to those of the other embodiments is omitted.

(Structure)

FIG. 32 shows a sectional view of a magnetic random access memoryaccording to the tenth embodiment of the present invention. FIG. 33shows a plan view and a sectional view in which a connecting portionbetween the MTJ element and the contact shown in FIG. 32 is enlarged.The magnetic random access memory according to the tenth embodiment ofthe present invention will hereinafter be described.

As shown in FIGS. 32 and 33, a contact 30 above an MTJ element MTJ issimilar to that of the first embodiment. That is, an area of a portionwhere the contact 30 comes in contact with a recording layer 13 via acap layer 20 a is smaller than an area of the recording layer 13. Thiscontact 30 is positioned at the center of the MTJ element MTJ (therecording layer 13).

A contact 40 under the MTJ element MTJ is similar to that of the secondembodiment. That is, an area of a portion where the contact 40 comes incontact with a fixed layer 11 via a cap layer 20 b is smaller than anarea of the fixed layer 11. This contact 40 is positioned at the centerof the MTJ element MTJ (the fixed layer 11).

Here, in the present drawing, the fixed layer 11 is arranged on atransistor Tr side and the recording layer 13 is arranged on aninterconnect 10 side, but the fixed layer 11 may be arranged on theinterconnect 10 side and the recording layer 13 may be arranged on thetransistor Tr side.

According to such a tenth embodiment, since the contacts 30, 40 aboveand under the MTJ element MTJ are small, spread of a write current I ina lateral direction is further suppressed. Therefore, a current path isfurther limited, and hence there is an advantage that an effect of a lowcurrent further improves.

[2] MTJ Element MTJ [2-1] Magnetization Arrangement

In the above embodiments, an example in which the fixed layer 11 and therecording layer 13 of the MTJ element MTJ are magnetized in a verticaldirection with respect to a film surface (a vertical magnetization type)has been described, but they may be magnetized in a parallel directionwith respect to the film surface (a parallel magnetization type).

It is to be noted that unlike a conventional example, the verticalmagnetization type of MTJ element MTJ has an advantage that themagnetization direction is not determined in accordance with alongitudinal direction of an element shape.

[2-2] Material

The MTJ element MTJ is made of, for example, the following material.

As a material of the fixed layer 11 and the recording layer 13, there ispreferably used Fe, Co, Ni or an alloy thereof as well as a magnetitehaving large spin polarizability, an oxide such as CrO₂ or RXMnO_(3-y)(R; rare earth metals, X; Ca, Ba or Sr), a Heusler alloy such as NiMnSbor PtMnSb, or the like. Each of these magnetic materials may contain aslight amount of a non-magnetic element such as Ag, Cu, Au, Al, Mg, Si,Bi, Ta, B, C, O, N, Pd, Pt, Zr, Ir, W, Mo or Nb, as long asferromagnetism is not lost.

As a material of the non-magnetic layer 12, a dielectric material suchas Al₂O₃, SiO₂, MgO, AlN, Bi₂O₃, MgF₂, CaF₂, SrTiO₂ or AlLaO₃ may beused. In these dielectric materials, an oxygen, nitrogen or fluorinedeficiency may be present. It is to be noted that in the cap layer 20 ofthe above embodiments, the above material of the non-magnetic layer 12may be used.

An antiferromagnetic layer for securing the magnetization direction ofthe fixed layer 11 may be provided on the surface of the fixed layer 11opposite to the non-magnetic layer 12. As a material of thisantiferromagnetic layer, Fe—Mn, Pt—Mn, Pt—Cr—Mn, Ni—Mn, Ir—Mn, NiO,Fe₂O₃ or the like may be used.

It is to be noted that examples of a vertical magnetic material forrealizing the vertical magnetization type MTJ element MTJ include thefollowings.

First, a magnetic material having such a high coercive field strengthfor use in the vertical magnetic material of the fixed layer 11 and therecording layer 13 is made of a material having a high magneticanisotropic energy density of 1×10⁶ erg/cc or more. Material exampleswill hereinafter be described.

EXAMPLE 1

“A material made of an alloy including at least one of iron (Fe), cobalt(Co) and nickel (Ni) and at least one of chromium (Cr), platinum (Pt)and palladium (Pd)”

Examples of a regular alloy include Fe(50)Pt(50), Fe(50)Pd(50) andCo(50)Pt(50). Examples of an irregular alloy include a CoCr alloy, aCoPt alloy, a CoCrPt alloy, a CoCrPtTa alloy and a CoCrNb alloy.

EXAMPLE 2

“A material having a structure in which at least one of Fe, Co and Ni oran alloy including one of them and at least one of Pd and Pt or an alloyincluding one of them are alternately laminated”

Examples of the material include a Co/Pt artificial lattice, a Co/Pdartificial lattice and a CoCr/Pt artificial lattice. In a case where theCo/Pt artificial lattice or the Co/Pd artificial lattice is used, as aresistance change ratio (an MR ratio), a large ratio of about 40% can berealized.

EXAMPLE 3

“An amorphous alloy including at least one of rare earth metals such asterbium (Tb), dysprosium (Dy) and gadolinium (Gd) and at least one oftransition metals”

Examples of the alloy include TbFe, TbCo, TbFeCo, DyTbFeCo and GdTbCo.

Moreover, the recording layer 13 may be made of the above magneticmaterial having a high coercive field strength. Alternatively, therecording layer may be subjected to regulation of a composition ratio,addition of impurities, regulation of a thickness or the like, and madeof a magnetic material having a magnetic anisotropic energy densitysmaller than that of the above magnetic material having the highcoercive field strength. Examples of the material will hereinafter bedescribed.

EXAMPLE 1

“A material in which impurities have been added to an alloy including atleast one of Fe, Co and Ni and at least one of Cr, Pt and Pd”

Examples of the material include a material in which impurities such asCu, Cr and Ag are added to a regular alloy such as Fe(50)Pt(50),Fe(50)Pd(50) or Co(50)Pt(50) to lower a magnetic anisotropic energydensity. The examples of the material also include a material in whichwith regard to an irregular alloy such as a CoCr alloy, a CoPt alloy, aCoCrPt alloy, a CoCrPtTa alloy or a CoCrNb alloy, a ratio of anon-magnetic element is increased to lower the magnetic anisotropicenergy density.

EXAMPLE 2

“A material having a structure in which at least one of Fe, Co and Ni oran alloy including one of them and at least one of Pd and Pt or an alloyincluding one of them are alternately laminated and in which a thicknessof a layer including the former element or alloy or a thickness of alayer including the latter element or alloy is regulated”

There is an optimum thickness of at least one of Fe, Co and Ni or thealloy including one of them, and an optimum thickness of at least one ofPd and Pt or the alloy including one of them, but the magneticanisotropic energy density gradually drops as each thickness departsfrom the optimum.

EXAMPLE 3

“A material in which a composition ratio of an amorphous alloy includingat least one of rare earth metals such as terbium (Tb), dysprosium (Dy)and gadolinium (Gd) and at least one of transition metals is regulated”

Examples of the material include a material in which a composition ratioof an amorphous alloy such as TbFe, TbCo, TbFeCo, DyTbFeCo and GdTbCo isregulated and in which the magnetic anisotropic energy density isreduced.

[2-3] Planar Shape

In the above embodiments, it has been described that a planar shape ofthe MTJ element MTJ is circle, but the present invention is not limitedto this shape. The planar shape of the MTJ element MTJ may variously bechanged to, for example, a rectangular shape, a square shape, anelliptic shape, a hexagonal shape, a rhombic shape, a parallelogramshape, a cross shape, a bean shape (a concave shape) or the like.

In the case of a parallel magnetization type of MTJ element MTJ, whenshape magnetic anisotropy is used and a minimum processing dimension (F)is assumed in a short direction (a magnetization difficult-axisdirection) of the MTJ element MTJ, the shape preferably has a dimensionof about 2F in a longitudinal direction (a magnetization easy-axisdirection).

In the case of a vertical magnetization type of MTJ element MTJ, sincethe magnetization direction does not depend on the shape, any of theabove shapes may be used.

[2-4] Tunnel Junction Structure

The MTJ element MTJ may have a single tunnel junction structure or adouble tunnel junction structure.

As shown in FIG. 1 and the like, the MTJ element MTJ with the singletunnel junction structure has a fixed layer 11, a recording layer 13,and a non-magnetic layer 12 provided between the fixed layer 11 and therecording layer 13. That is, the MTJ element MTJ has one non-magneticlayer.

The MTJ element MTJ with the double tunnel junction structure has afirst fixed layer, a second fixed layer, a recording layer providedbetween the first fixed layer and the second fixed layer, a firstnon-magnetic layer provided between the first fixed layer and therecording layer, and a second non-magnetic layer provided between thesecond fixed layer and the recording layer. That is, the MTJ element MTJhas two non-magnetic layers.

In the double tunnel junction structure, as compared with the singletunnel junction structure, a magnetoresistive (MR) ratio (a change ratioof a resistance in a “1” or “0” state) at a time when the same externalbias is applied little deteriorates, and the structure can operate witha higher bias. That is, the double tunnel junction structure isadvantageous in reading data from cells.

[3] Effect

According to the above embodiments of the present invention, in thecontact to be connected to at least one end portion of the MTJ element,an area of this contact which comes in contact with the recording layeris set to be smaller than that of the recording layer. Therefore, duringa write operation, the magnetization reverses from a local contactportion between the contact and the MTJ element, and the magnetizationreverse is propagated owing to a magnetic wall movement effect, wherebythe magnetization of the whole element reverses. Therefore, a currentwhich flows through the MTJ element during the write operation can bereduced. Furthermore, the cap layer having a resistance higher than thatof the recording layer is provided, so that reduction of an effect dueto current dispersion can be prevented.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

1. A magnetic random access memory comprising: a magnetoresistive effectelement which includes a fixed layer having a fixed magnetizationdirection, a recording layer having a reversible magnetization directionand a non-magnetic layer provided between the fixed layer and therecording layer and in which the magnetization directions of the fixedlayer and the recording layer are brought into a parallel state or ananti-parallel state in accordance with a direction of a current flowingbetween the fixed layer and the recording layer; a first contact whichis connected to the recording layer and in which a contact area betweenthe recording layer and the first contact is smaller than an area of therecording layer; and a cap layer which is provided between the firstcontact and the recording layer and which directly comes in contact withthe first contact and which has a resistance higher than a resistance ofthe recording layer.
 2. The memory according to claim 1, wherein aplanar shape of the magnetoresistive effect element and the contact iscircle, and a diameter of the contact is smaller than a diameter of themagnetoresistive effect element.
 3. The memory according to claim 1,wherein an area of the cap layer on the side of the first contact islarger than an area of the first contact on the side of the cap layer.4. The memory according to claim 1, wherein the first contact ispositioned above the magnetoresistive effect element.
 5. The memoryaccording to claim 4, further comprising: a first insulating film formedaround the magnetoresistive effect element and the first contact andhaving, on the magnetoresistive effect element, a groove having a sizeequal to a size of the magnetoresistive effect element; and a secondinsulating film formed only on a side surface of the groove and made ofa material different from a material of the first insulating film, thegroove being filled up with the first contact.
 6. The memory accordingto claim 1, wherein the first contact is positioned under themagnetoresistive effect element.
 7. The memory according to claim 6,further comprising: a first insulating film formed around the firstcontact and having a groove; and a second insulating film formed only ona side surface of the groove and made of a material different from amaterial of the first insulating film, the groove being filled up withthe first contact.
 8. The memory according to claim 1, wherein a hollowportion is formed at a center of the first contact.
 9. The memoryaccording to claim 8, wherein an outer side surface of the first contactcoincides with a side surface of the magnetoresistive effect element.10. The memory according to claim 8, further comprising: a firstinsulating film formed around the magnetoresistive effect element andthe first contact, having, on the magnetoresistive effect element, agroove having a size equal to a size of the magnetoresistive effectelement, and provided with the first contact only on a side surface ofthe groove; and a second insulating film formed in the hollow portionand made of a material different from a material of the first insulatingfilm.
 11. The memory according to claim 8, further comprising: a firstinsulating film formed around the first contact, having a groove, andprovided with the first contact only on a side surface of the groove;and a second insulating film formed in the hollow portion and made of amaterial different from a material of the first insulating film.
 12. Thememory according to claim 1, wherein an area of the first contact isequal to an area of the magnetoresistive effect element, and a center ofthe first contact shifts from a center of the magnetoresistive effectelement, the contact area between the first contact and the recordinglayer is reduced.
 13. The memory according to claim 1, wherein an areaof the first contact is smaller than an area of the magnetoresistiveeffect element, and a center of the first contact sifts from a center ofthe magnetoresistive effect element.
 14. The memory according to claim1, wherein the first contact has linear first and second portionsdisposed away from each other.
 15. The memory according to claim 1,further comprising: a second contact connected to the fixed layer, acontact area between the fixed layer and the second contact beingsmaller than an area of the fixed layer.
 16. The memory according toclaim 1, wherein during a write operation, magnetization of therecording layer reverses from a portion where the first contact comes incontact with the recording layer, and the whole magnetization of therecording layer reverses owing to propagation of the magnetizationreverse.
 17. A magnetic random access memory manufacturing methodcomprising: forming a magnetoresistive effect element having a fixedlayer having a fixed magnetization direction, a recording layer having areversible magnetization direction and a non-magnetic layer providedbetween the fixed layer and the recording layer; forming a firstinsulating film on the magnetoresistive effect element; covering thefirst insulating film with a second insulating film and removing thesecond insulating film until the first insulating film is exposed;removing the first insulating film to form a groove; forming a thirdinsulating film only on a side surface of the groove; and forming acontact in the groove, a contact area between the contact and themagnetoresistive effect element being smaller than an area of themagnetoresistive effect element.
 18. The method according to claim 17,further comprising: forming, between the contact and themagnetoresistive effect element, a cap layer having a resistance higherthan a resistance of the recording layer.
 19. A magnetic random accessmemory manufacturing method comprising: forming a magnetoresistiveeffect element having a fixed layer having a fixed magnetizationdirection, a recording layer having a reversible magnetization directionand a non-magnetic layer provided between the fixed layer and therecording layer; forming a first insulating film on the magnetoresistiveeffect element; covering the first insulating film with a secondinsulating film and removing the second insulating film until the firstinsulating film is exposed; removing the first insulating film to form agroove; forming a contact having a hollow portion at the center thereofonly on a side surface of the groove, a contact area between the contactand the magnetoresistive effect element being smaller than an area ofthe magnetoresistive effect element; and forming a third insulating filmat the hollow portion.
 20. The method according to claim 19, furthercomprising: forming, between the contact and the magnetoresistive effectelement, a cap layer having a resistance higher than a resistance of therecording layer.